Field of the Invention
The present invention relates to a sole and a shoe.
Background
Many modern sport shoes include shoe soles including foamed materials. For example, foams made from ethylene-vinyl-acetate (EVA) or polyurethane (PU) provide excellent cushioning properties for the loads arising in a shoe sole and are therefore used as a typical material for a midsole, which is arranged between an insole region and an outsole region of a shoe sole.
The lifetime of midsoles made from foamed materials, however, is rather limited. Irreversible degradations of the foamed materials under repeated compression and shearing loads on the sole are the reason that initially good cushioning properties are quickly lost. As a result, the sport shoe is “worn-out” and no longer meets the requirements of cushioning and biomechanically supporting the foot.
Furthermore, the dynamic properties of the foamed materials are strongly temperature dependent, which causes problems, in particular for sports (e.g., running) performed outdoors in cold weather, as the foamed material becomes hard, thus diminishing its cushioning properties. A further disadvantage of the use of foamed materials is the limited possibilities to adapt the cushioning properties to the size of a shoe and the expected weight of the wearer. Also, at smaller shoe sizes the surface portion of the foamed material is larger in relation to the volume, thus leading to lower temperatures of the foamed material (i.e., an undesirable hardness) when subjected to low-temperature environments. Modifications in sole constructions beyond the use of midsole layers of different thicknesses can only be realized, in mass production, through high effort and high cost.
Therefore, a number of approaches are known in the art to at least partly replace midsoles made from foamed materials.
For example, German Patent Application No. DE 10 2006 015 649 discloses arranging cushioning elements made from a thermoplastic urethane (TPU) below a sole area, which elements do not comprise foamed materials. U.S. Patent Application Publication No. 2007/0209230 further discloses sole constructions, wherein a plurality of curved spring elements is arranged in the sole area, all of which have essentially the same orientation. U.S. Pat. No. 5,185,943 shows a cushioning insert serving as reinforcement and being integrated into an otherwise common midsole of a shoe.
The known constructions, however, are not able to provide the advantageous cushioning properties of a new midsole made from foamed materials. Furthermore, the constructions mentioned in the last two documents are very complex to manufacture and for this reason are not practically used.
Further, U.S. Patent Application Publication No. 2002/0038522 A1 describes soles with cavities in which support members are placed that return towards their original shape when deflected by an external force. U.S. Pat. No. 6,925,732 B1 describes a sole structure with a frame element. The frame element extends around a heel portion and serves as a spring element in combination with the midsole. Finally, U.S. Patent Application Publication No. 2009/0178303 A1 describes a sole assembly with an upper plate and a lower plate in a forefoot portion of the sole assembly, and a plurality of lower plate arms curving downwardly from the upper plate.
Embodiments of the present invention are therefore based on the problem of providing a sole construction that can be easily manufactured, that uses minimal foamed materials, and that can be economically manufactured in order to at least partly overcome the above-mentioned disadvantages of the art.